Combination process



G. D. VAN ARSDALE COMBINATION PRoCEss Filed S'p'b. 2.8' 1923 Sept l5, 925.

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sxm bin bwhnwwmdw Patented Sept. 15, 1925.

UNITED4 STATES PATENT ori-"lon,y

GEORGE D. VAN ARSDALE, OF LOS ANGELES, CALIFORNIA, ASSIGNOR TO INSPIRATION CONSOLIDATED COPPER COMPANY, 0F NEW YORK, N. Y., A CORPORATION OF MAINE.

COMBINATION PROCESS.

Application led September 28, 1923. Serial No. 665,463.

To all whom t may concern:

Be it known that I, GEORGE D. VAN ARS- DALE, a citizen of the United States, residing at Los Angeles, in the rcounty of Los Angeles and State of California, have 1nvented new and useful Improvements in a Combination Process, of which the follown is a specification.

y present invention relates to a process of recovering values from ores and other materials which is especially applicable to copper-bearing materials and which certain recentl, discovered methods of leaching and electro eposition, as set forth in my ap- -plication covering a method of leaching sulfd and mixed ores, Serial No. 639,969, filed May 18, 1923, may be advantageously combined in a comprehensive procedure comprising also, as one of' its essentials, a new method of recovering residual values by a countercurrent Washing followed by an exhaustivewashing involving a precipitation, this novel method of Washing being described and claimed in a joint application by Harold WV. Aldrich, Walter S. Scott and myself, Serial No. 661,531``1led Septem-4 ber 7, 1923.

My present combination process is especially designed to render commercially available certain large bodies of ore for the treatment of which no commercially profitable method is `known to have been heretofore developed; and this combination process may optionally be employed also in connection with the novel method of treating concentrates by steps comprising a deferred 1o: 1sting, or entirely omitting roasting, as

i set forth in my copending application Serial No. 639,968, also tiled May 18, 1923.

My present invention is directed especially to the treatment of that class of copper ores known as mixed ores, or of so called oxidized ores, but other materlals such as oresl or concentrates containing copper Wholly or partly in snltid form may be treated, various alternative stepsheing hereinafter suggested as applicable according to the conditions encountered. It may be further stated by Way of general introduction that this process aims to so utilize and coordinate ,the essential features of the mentioned novel Washing method with the essential features of a cyclical method involving a leaching and an Y electrodeposition that both a solution of copper salts obtained b a countercurrent washing and a copper bearing precipitate obtained by an exhaustive Washing involving cementation of copper shall effectively supplement `and combine with rich liquors from which total copper may be recovered by electrolysis; and, in one embodiment of my invention Whichpis especially suitable to cyclicaly processes employing an' iron salt as a solvent of copper values, the mentioned exhaustive Washing may be soexecuted as to yield, incidentally to the very complete recovery of copper by thenovel Washing system, a solution containing iron salt suitable for use in maintainingv the ferrie content of a leaching agent cyclically regenerated during 'an electrodeposition,bothl the leaching and the electrodeposition being optionally conducted, under a novel technique described in my application first above mentioned and also described herein, in the presence of ferrie iron in such quantities as may be found most favorable to a maximum efficiency in leaching.

As a concrete example of the application of. my discoveries in a process of treating mixed copper ores, I may refer, as in. my prior application, to the treatment of a body of dry crushed ore adapted to pass through a one-third or a one-fourth inch mesh. `Suitable crushing is highly important to the best success in the application of my process to materials containlng copper in sulfid form, as it may contribute not only to a completenessof recovery but may also obviate the necessity for'an application of heat during leaching, or it may materially shorten the period of treatment.

Broadly, the process to which I subject successive bodies l'of such dry crushed ores or other copper bearing materials preferably involves a percolation method of extraction so associated with a novel method of Washing and. a method of electrodeposition that the latter may yield metallic copper, and' present during electrolysis and during extraction.

' When values are to be recovered from mixed ores of the specific character just referred to, or from certain types of concentrates containing copper in sultid form, I may subject a body of suitably subdivided material, without roasting, to treatment in an aqueous solvent containing, in addition to about 5% sulfuric acid, more or less, depending on the character of the ore, about 0.5% to 1.5% of iron in the form of ferrie sulfate and copper in the form of copper sulfate, which may be present in quantities from about 2.5% to about 4.5%.

'.h'e reactions and methods by which the oxi i constituents are dissolved, as above indicated, do not materially differ from known acid leaching practice on these constituents; but it had not been considered practicable, prior to the discovery set forth in my application first above mentioned. to remove both oXid andsulfid compounds by one leaching operation.

It had been known that sultidcompounds of copper are amenable to the solvent action of ferrie salts under certain conditions. The

following equation is an example of such ac- Y tion, in the presence of free acid sutiicieiit to prevent precipitation of `compounds of 1ron:

It had also been known that the solution produced by. the above equation may be treated by electrolysis so as to regenerate the solvent. There had, however, been other obstacles, unrelated to the above mentioned discovery of the necessity for fine crushing, inthe way of a practical application of the above simple method of leaching sulfur compounds with ferrie iron and subsequently regenerating the solvent. Up to the time of my mentioned discovery, 'electrolysis of coplpersulfate solutions carrying iron had not een found practicable, without a diaphragm cell, when the strength of ferrie 1ron incidentally produced during electrolysis rose above a figure in the neighborhood of 0.3% to 0.5%.

But, as I have pointed out in my mentioned application, solutions carrying only.

0.3% to 0.5% ferrie iron are comparatively inactive on some sulfide compounds of copper; and, on others, the action is slow and success may depend upon heating. With solutions containing higher amounts of fer-D rie iron, say from0.5% to 1.5%, I discovered that the solvent action is. muchmore active and rapid; so that, on some ores and concentrates, the necessity for any warming of the solutions is obviated,-with very substantial economic advantages. It will be undel-stood from the foregoing that, in the employment of ferrie sulfate leaching solutions, starting with, say 1% or more of ferric iron, complete reduction of ferrie iron during such leaching and before electrolysis cannot be economical, from the standpoint of leaching eiliciency,although this complete reduction had, prior to my mentioned discovery, been regarded as essential to good electrolytic practice.

In addition to the discovery just referred to, my first above mentioned application sets forthalso the important complementary discovery that, by modifying electrolytic conditions, electrolysis can be carried on, with commercial yields of copper, in the presence of very much higher amounts of ferrie iron than have heretofore been thought permissible, and even in the presence of an amount suiliciently high to constitute an active solvent percentage of ferrie iron. I have therefore proposed to use conjointly, and have recently used with marked success, my respective discoveries that such solutions are high ly active solvents and that it is practicable to 1 make them by electrolysis; and, to do this, I

prefer to leach the ore in such manner as not to obtain a substantially complete reduction of the ferrie iron present, aiming rather to so proportion ore or concentrate and solvent that a good extraction shall take place during a period within which the percentage of ferrie iron present in the solvent or 'leach liquor is still high enough to actvigorously. This point will,y of course, vary |with different materials and conditions; but, in general, I have found it not necessary to reduce ferrie iron below about 0.2%, and, in some cases, not below 0.5%. Generally speaking, on most ores, a maximum strength of 1% of ferrie iron`is sutlicient for high leaching eficiency; but higher percentages may be used, if necessary; and a preferred method by which such percentages of ferrie iron may be made by electrolysis, as set forth in my mentioned application, is also referred 'to subsequently herein.

`a rich liquor suitable for ele-:"= 'olysis` will vary with the character of the ore and may be from four to twelve days. The use of the described relative content of ferrie iron in the leach liquor makes possible the indicated `reliance u on a comparatively short period of extraction, and may obviate the necessity for an application of heat, even during the final period oft-extraction. As `is now customary in operations of this character, the countercurrent principle is preferably employed throughout the leaching; and, whenever such a course shall be indicated by a comparison of the coppercontent of the ore with the assay of a regenerated solvent resulting from eleetrolysis,'as hereinafter described, suitable additions of acid or ofc.

solution containing iron salts obtained as hereinafter mentioned may be made to the leach liquor; but otherwise it is of importance that the volume of successive portions of leach liquor be so controlled as not mate* rially to change the total yolume of solution. This can be done by well known methods provided there is no excess or deticiency of solution constituents. In case the cyclical treatment of 'successive charges of ore causes an undue accumulation or building up of any metal, a solution discard for special treatment may be required, or other described methods of readjnstment may be employed; but, in any event, the invention to which the present application is directed must be regarded as'involving a completion of recovery by the newly discovered washing method involving both a countercurrent Washing and a. circulation or -'exhaustive Washing in the general manner set forth in i vthe joint application above mentioned.

lFor example, in washing by percolation, a number of successive washes are applied, each of which removes a fraction of the remaining copper. Assuming that it is desirable to have the volume of the respective washings so adjusted that the total volume of solution remains practically ay co-nstant,

the unit volume of washivater may be ad- `justedftobe' approximately equal to the volume of liquid finally discharged, as residual moisture, 1n the tailings, allowance bemg made for such moisture as comes mto the system with the ore, and for evaporation during the cycle of operations. llVhen the total volume'of solution is controlled in the manner just referred to, the Strongest wash water being finally added to the main body ofrich liquor obtained by' leaching, the subsequent washes are successively. advanced,

It is not practicable to carry more. than a. limited number of stock washes,-and even when lsix or eight washes are employed, the last wash may carry from 0.15% to 0.25% or more of copper. Discharge of tailings carrying residual moisture with such percentages of copper results in appreciable losses. The above mentioned joint application `accordingly makes use of the fact that it is often per-- fectly practicable and economical toprecipitate copper, for example by cementation, from solutions carrying much less than the above mentioned perdentages, the economy of such a precipitation being due to the facts that pumping costs are ordinarily com paratively low and that cementation costs are per-pound costs. There thus arises an especial advantage in the employment of the exhaustive method of washing, involving cementation, as a supplemental procedure following the employment of a countercurrent method; In connection with the new system of washing just referred to and described and claimed in the mentioned joint application, it is pointed out that the novel method of washing here referred to may ola-H viously be applied in conjunction with various methods of leaching ores, or the like, for example agitation methods of leaching; but it should also be appreciated'that there are special additional advantages in so employing this novel washing method that, it shall v'economically contribute (l) to a. completeness of copper recovery by providing both a wash liquid and a precipitate suitable for addition to the rich liquors and also (2) lto the replenishment of the iron salts required in the leach liquors, in the manner herein described.

As -applied in connection with a leaching of copper bearing materials by percolation, my novel combined process may be further illustrated as follows: i

Batches of approximately forty tons of mixed ore assaying about 1.5% total copper (of which, for example., 0.88% may be acid soluble and 0.02% may be in sultid form) have been crushed to about one-third inch mesh and distributed to a depth of approximately fifteen feet in the bottom of substantially rectangular concret-e tanks, within which they have been treated by a countercurrent percolation method of the character above referred to for a contact period of approxi mately ten days, employing an acid ferrie sulfate liquorcarrying 'between 1.00% and 1.5% of ferrie iron initially, und about 5% free sulfuric acid, and about 2.75% of'copper as sulfate. This mentioned treatment by percolation was then Vfollowed by a draining 0f theore. and by a washing on the countercurrent principle in the manner outlined above, about forty gallons of water per ton of ore being employed as al unit volume of wash liquor, and tive or six similar unit volumes of wash liquor being successively applied to a. batch of ore, and each first or strongest wash liquor being tinally added to the rich. liquor for electrolytic treatment. and the others advanced for subsequent washing as hereinafter described. After the draining of the last unit volume of wash.

liquor from the ore, water, in any quantity suitable to convenient manipulation, was'` leo l leaching as described, countercurrent washing and exhaustive washing as described, and discharging: Total copper 0.159%, including soluble copper 0.005% (all of this .005% being water soluble) and sulfid copper 0.154%. In the case of the materials referred to, this was equivalent to extraction percentages as follows:

v 11i-recht. Total copper 89.4 Soluble copper 99.2 Sulfid copper 75.1

As will be understood, the described procedure yields not only, by the countercurrent washing, wash liquor finally suitable to be added to the rich liquor and a precipitate of cement copper also suitable to be added thereto, for a final recovery of total copper by electrolysis or other desired means, butalso the mentioned solution of iron salts resulting from the cementation; and it will be understood that any suitable quantity of the circulating Wash liquor used in the mentioned exhaustive washing may at any time be added to the leach liquors, as `may be indicated by the assay of the respective liquids referred to, the conservation of iron salts here referred to being optionally supplemented by a final 4washing of tailings with water to effect a further removal therefrom of iron salts introduced or augmented there- ,in by the described exhaustive washing.

Before outlining the technique by which I prefer to obtain copper values from my rich liquors, I now refer to certain variations of procedure by which my combination process above outlined 'may be best adapted to the utilization of certain specific copper bearing materials. It being well known that a preliminary roasting is advantageous in the case of many ores, I mention at this point my recent discoveries regarding an alternative treatment of concentrates, as set forth in my patent application Serial No. 639,698, filed May 18,1923, in which I have pointed out that, although an initial roasting of certain concentrates, which may contain, for example, bornite, or chalcocite, or chalcopyrite, may yield a calcine whose extraction is very incomplete, the employment of an initial leaching, followed by what I have termed a deferred roasting, may yield, with the same material, a calcine from which a nearly complete extraction is possible.

When use is made of a preliminary leaching followed by a deferred roasting and a subsequent leaching, successive portions orv unit quantities of the respective leach liquors may be employed upon the countercurrent principle, as outlined above, and an application of heat, especially toward the end of the extraction, may be sometimes. economically justified, the necessity for heat or without an application of heat, being y often insufficient for a satisfactorily complete recovery of values. The residue being then separated, by filtration or otherwise, from the leach liquor, I may roast this residue Without risk of the detrimental effect referred to above, the leached concentrates being thereby brought largely into an oxidized condition favorable to a very complete extraction, the resulting filtrates'being optionally combined with those first obtained, and all washings, following this second extraction, being executed in the novel manner above set forth in detail, the total and augmented .quantity of rich liquor being finally subjected to an electrolysis or to other treatment adapted to the production of either metallic copper or a desired compound thereof, but preferably to an electrolysis especially suitable to a maximum eiiiciency of extraction in the combination and cyclical process upon which protection is herein sought.

Although what Ihave above described as a deferred roasting is often distinctly more advantageous than an initial roasting and may be employed for leaching concentrates, it is of the highest technical and practical interest that, in the case of certain ores carrying sulfid copper, I find it possible and economically advantageous actually to dispense with all roasting, a suitable recovery being obtainable without this` expensive step. Itwwill be obvious that, whenever liquors representing a good recovery and suitable for use in my novel dissolving and washing and electrolytic process are obtainable by a mere cold extraction (or by a cold extraction followed by a warm extraction,- depending on the nature of the sulfids present) this last mentioned variation of my process, favorable to a working of extensive bodies of ore that have been regarded as' 'nsy sus`

Both the copper-containing precipitatel which is obtained by cementation and the washings obtained by the counter-current method referred to being combined, at any suitable intervals, with the rich liquors obtained as described above, one very important practical feature common to my invention described in the prior application first above mentioned and the present a plication is the method of electrolysis by w iich I may produce or regenerate larger amounts of ferrie iron than have hitherto been thought possible at any reasonable cathode efficiency. Contrary to the prevalent opinion, I have found, asset forth in my mentioned application, that commercial yields of copper per kilowatt hour may be had average percentage of ferrie iron before and after electrolysis. ln operating with a comparatively high average of ferrie iron, there- `fore, the solutions have to be returned more frequently, in order to leach the copper from l any given quantity of ore. This is done at an expense of pumping cost; but may nevertheless be entirely justified in view of the fact that, as stated, high ferrie iron is very desirable from the standpoint of leaching elliciency.

ln order to obtain commercial cathode eliiciency during electrodeposition of copper, l have found it necessary to employ a current density of at least seven to eight am- .lili

peres per square loot, and the current den* sity may be raised to fifteen amperes or more per square foot; and l have found that, by suitably proportioning current density to ferrie iron, the latter may be disregarded. To obtain commercially protable yields, as measured in terms of pounds of copper per kilowatt hour, it is also important that low voltages be obtained: and a suitable lowering of voltages by an increase in conductivity may be obtained by a moderate heat ing (say, to 110 F.) in connection -With which it is necessary to employ known means of depolarization, and it may be necessary to employ as many graphite anodes as may `loe suitable to a desired ratio ot conversion et iron salts into the ferrie form, as de-v scribed in my copending application 639,970, also tiled lilay 18, 1923, but to vvhich'the present application may be regarded as not necessarily related.

All of the alternative procedures to the protection 'of which my present application is directed ivill be understood to involve a novel Washing method employed subsequently to a leaching and previously to a final recovery of copper by a process in which a leach liquor may be regenerated, the limiting` case, as to Washing methods, being that in which a4 circulating or exhaustive wash, involving a precipitation of copper, may constitute practically the only method ot Washing relied on; and this limiting case should regarded as falling cti? within thescope of my present invention whenever the mentioned precipitate containing copper is added to a rich liquor for recovery of total copper by my novel method of electrodeposition, ory Whenever a liquid containing iron salts obtained by coincntation is added to a leach liquor for further usc. The accompanying drawing is a flow sheet of the process. The ore passes from thev niine to the coarse crushing plant thence to storage bins B and to the fine crushing' and screening plant C and finally to the sampling plant D whence it passes to the leaching tanks indicated as a Whole at .ll and numbered in succession 1, 2, 3, 4f, (l. i and Fw'. ln the actual operation, siX of those tanks are used at any one time, five for leaching, passing the solution through them inV succession` one lfor Washing and one for loading. At. the stage illustrated a fresh batch ot' orc is being loaded into the tank 6, numbers 1 to 45 being used for the leaching operation. The rich liquor passes from tank No. 5 by the line F to the copper solution storage tank G, thence my the line H to the tank house K where the electrolytic operation is performed and the cathode copper is removed by the line la. The regenerated acid solution from the tank house l passes by the line lil to an acid' solution storage tank N and thence by the line 0 to the rst et the leaching tanks in use. Additional acid is supplied from a suitable reservoir by the line J leading into the line ll.

There are six` tanks for the storage 0l the advancing Wash Water indicated as a lltill Whole at l)` and numbered in succession from 1 to 6. llresh water comes into the leaching tank 7 containing the residual ore after leaching, by Way of the line Q5. rlhe Wash wat-er circulates inl turn between the tank 7 and the Wash storage tank 6 by Way oit lines ll thence between leaching tank T and vvash storage tank 5; thence between leaching tank 7 and wash storage tank Ll; and so forth, to the end until it is at a maximum practicablerichness; whereupon it is passed by the line-'Si into the line ll containing the` copper solution to be treated electrolytically.

The 'llo-iv of theadvancing Wash storage is then stopped and the material in the tank is treatet; to the circulating Wash storage. The Water circulates through the tank 7 and the circulatingvvash storage tank T by Way oit the lines ll, a portion beingz taken olli continuously by Way of the line V to the cement copper plant WV and passing thence bythe line back into the circulating' body et Wash Water. lf 7hen the maximum extraction has been obtained in this Way, 'the tailings are removed-by the line Y.

During the above operation it. is understood thatithe leaching tank 8 is full ci leached residues. The Washing process is .lill

lillli eration to the tank 7, the leaching operation to tanks 2to 6 in succession, while tank 1 is left idle. It willalso be 'understood that, both the familiar and the original component features of my combination process being lcapable of numerous independent uses, a great many variations or modifications of my preferred procedure, additional to those herein sug ested, will fall clearly within the scope of t e present invention, as the same is outlined above and in the apy pended claims.

What I claim is: 1. In the recovery of copper, the steps which comprise leaching ores by means of a tities of leac -liquor and finally recovering.

total `cop er by an electrodeposition.

3. In t e recovery of cop er from 'materials containing the same in sulfidform by a cyclical process involving an extraction which tends to convert ferrie iron into ferrous iron and an electrodeposition which tends to convert ferrous iron into ferrie iron, the procedure which comprises washing leached residues by a countercurrent method followed by an exhaustive method and main- .taining the ferrie iron throughout both said leaching and said`electrodeposition at a level determined by the efticiency vof extraction,

up to 1% .or more of ferrie ironbeinoP tolerated durin the electrode osition of copper, and said electrodeposition being conducted under conditions of current density permitting the percentage of ferrie iron present to be disregarded.

4. In the recovery of values` from materials containing. copper, the rocedure which comprises an original-leac in followed by a roasting and a subsequent l(leaching of said materials in a leach liquor containing iron salts,'to obtaina rich liquor, washing the leached residues by the use of a countercurrent method followed by an` exhaustive method yielding a preci itate containing copper and a solution o `iron salts, and utilizing a portion of the nientioned solution of iron salts in the leaching of additional quantities of materials.

5.I In the recovery of values from mayterials containing copper, the procedure which comp-rises an original leaching followed by a roasting and a subsequent leaching of said materials in a leach liquor containing iron salts, to obtain a rich liquor, washing the leached residues by the use of a countercurrent method followed by an eX- haiistive method yielding a precipitate containing copper and a solution of iron salts, and utilizing a portion of the mentioned solution of iron salts in the leaching of additional quantities of materials, wash waters being added to rich `liquors for joint treatment by electrolysis.

6. In the recovery of 4values from materials containing copper, the procedure which comprises an original leaching followed by a roasting and a subsequent leaching of said materials in a leach liquor containing iron salts, to obtain a rich liquor, washing the leached residues by the use of a countercurrent method followed by an exhaustive method yielding 'a' precipitate containing copper and a solution of iron salts, and utilizing a portion of the mentioned solution of iron salts in the leaching of additional quanties of materials, wash Waters being added to rich liquors for joint treatment by electrolysis, the mentioned precipitate being added to the rich liquors for recovery of total copper therefrom.

precipitated by cementation to a rich liquor.

8. In the recovery of copper values, the method which comprises circulating a wash liquid through a body of leached material and precipitating copper from said liquid 'by cementation, repeatedly returning said wash liquid until the removal of copper values shall have been carried to adesired degree of completeness, and utilizing a portion of the circulating wash liquid, after copper has been precipitated therefrom, in the preparation-.of a leach liquor.

9. In the recovery of copper values by ste s comprising la leaching in an acid solution of iron salts, the method which comprises an exhaustive Washing by which such salts'are formed and an addingof the soformed salts to a leach liquor.

10. In the recovery of copper values by steps comprising a leaching in an acid solution of iron salts, the method which comprises an exhaustive washing by which such 'salts 'are formed and an adding of the so-formed salts to a leach liquor,.the mentioned leaching being initiated in the presenc; of ferrie iron amounting to more than 0.5 a.

11. In the recovery of copper values by steps comprising a' leaching in an acid solution of iron salts, the method which comprises an exhaustive Washin by which such salts are formed and an a ding of the soformed salts to a leach liquor, said exhaustive Washing for the recovery of copper being followed by an additional washing for the conservation of iron salts. y

12. In the recovery of copper values by steps comprising a leaching in an acid solution of iron salts,- the method which comprises an exhaustive Washing by which such salts are formed and an adding of the so-ormed salts to a leach liquor, total copiper being finally recovered by an electroysls. y

13. Inthe recovery of copper values by steps comprising a leaching in an acid solution of iron salts, the method which comprises an exhaustive Washing by which such salts are formed and an adding of thesoformed salts to a leach liquor, total copper being finally recovered by an electrolysis conducted under conditions of current densalts are formed and an adding of the soi formed salts to a leach liquor,l total copper being finally recovered by an electrolysis conducted under conditions of current density permitting the percentage of ferric iron present to be disregardedl and -by means of anodes favorable toa desired percentage 'of ferrie iron in a regenerated leach liquor.

15. In the recovery of values by wet methods of treatment from ores or'rthe like the steps vWhich comprise dissolving fthe values, Washing the residues by a countercurrent method, thereafter Washing the same residues byan exhaustive or circulation method yielding a part of the solvent and employing the resulting liquid in the prep- .aration of additional quantities of solvent.

In testimony whereof I have signed my name to this specification.`

GEORGE D. VAN ARSDALE. 

